Doppler limited laser spectroscopy on hafnium lines. Part I: Hyperfine structure of even-parity levels

High-resolution Doppler limited hyperfine structure investigations done by laser spectroscopy techniques using laser induced fluorescence and optogalvanic detection are performed in the plasma of a liquid nitrogen cooled hollow cathode discharge in the atomic spectrum of Hafnium on selected lines in the red spectral region. Hyperfine structure spectra obtained using an enriched sample of 177Hf yielded hyperfine structure constants A and B of both transition levels. For the first time, an experimentally derived description of the levels of the $5d^36s$ configuration are presented. Combined with previously obtained data, the hyperfine structure of altogether 12 fine structure levels has been analysed by the simultaneous parametrisation of the one- and two-body interactions in the atomic hyperfine structure for the model space $(5d + 6s)^4$.The radial parameters of the magnetic dipole and electric quadrupole interactions are determined for the configurations $5d^26s^2$, $5d^36s$ and $5d^4$ and compared with ab initio calculations. Finally a complete list of the predicted hyperfine structure constants A and B of all levels of the system was generated